A wall pockmarked by bullet holes from a WWII battle in Budapest, HungaryMedieval walls line a street in the village of Durnstein, AustriaThe walls of a lock on the Rhine Main Canal in Germany. This lock gave an 80-ft elevation changeHandprints decorate an ancient Mayan wall in the old city of Tulum in MexicoFire escapes on the outside walls of 19th century builds in Little Italy, New York City